This invention relates to an apparatus for treating tail yarns in textile spindle assemblies of textile spinning machines, twisters or the like, more particularly to the improvement of an apparatus for holding and automatically releasing tail yarns, for example, separated ends of yarns wound on bobbins including portions interconnecting the bobbins and spindle assemblies.
When the doffing operation for changing completed yarn packages to empty bobbins is automatically conducted by using auto-doffers in textile spinning machines, twisters or the like, it is necessary to securely fix each tail yarn wrapped several turns on a tail yarn winding portion formed on a base portion of a spindle so as not to move for the purpose of making sure the automatic yarn winding on the bobbin. If it happens that yarn underwindings formed on the tail yarn winding portion move by a slight force, the yarn underwindings are loosened on rising of a ring rail to a position where the yarn is wound on the bobbin, which causes the disordered position of a traveler. Consequently, yarn breakages are liable to occur at the start of the operation.
The greatest cause of hindering the tail yarn from the secure fixing on the tail yarn winding portion is the presence of the yarn underwindings wound on the tail yarn winding portion. Namely, the tail yarn is wrapped several turns on the tail yarn winding portion such as a knurled surface formed on the base portion of the spindle so as not to move. However, an interconnecting yarn formed between the bobbin and the tail yarn winding portion is separated on the subsequent doffing operation, and a new tail yarn is further wrapped several turns on the yarn underwindings remaining on the tail yarn winding portion to repeat the doffing operation. A new tail yarn is wrapped several turns on the yarn underwindings on all such occasions.
When a new tail yarn is further wrapped on the yarn underwindings which are residual tail yarns previously wrapped, the fixing effect of the yarn underwindings by the knurled surface and the like is lost, which permits the yarn underwindings to move by a slight external force, thereby loosening the yarn underwindings.
Previously, in order to eliminate such inconvenience, the yarn underwindings have been periodically manually removed by use of a cutter or the like while the machine is stopped. However, such a prior-art method is reduced in the operation efficiency of the machine, because the operation is complex, labor intensive and time-consuming.
Then, for the purpose of solving such problems of the prior art to securely fix the tail yarn on the base portion of the spindle and to surely remove the yarn underwindings during the machine operation, the present invention has formerly proposed an apparatus for treating the tail yarn which comprises an upper slit ring fixedly mounted on the base portion of the spindle, a cylindrical member having a lower slit ring at an upper end thereof and a lower portion outwardly expandable by centrifugal force, and a guiding surface fixed on a lower part of the base portion of the spindle, the cylindrical member being axially slidably fitted on the base portion of the spindle beneath the upper split ring and mounted so that a lower end of the expandable portion thereof capably comes into contact with the guiding surface, the upper slit ring and the lower slit ring being pressed together to form a tail yarn gripping means, whereby the expansion of the lower portion of the cylindrical member by centrifugal force causes the cylindrical member to slide axially downward to release a pressed state between the upper slit ring and the lower slit ring (U.S. Pat. No. 4,796,442).
However, in the use of such an apparatus, the lower portion of the cylindrical member gets fatigued by repetition of its expansion and restoration to weaken the restoring force thereof upon standstill of the spindle, which results in an decrease in the pressing force of the lower slit ring to the upper slit ring, whereby it happens that the tail yarn can not be securely fixed to the tail gripping means.